EQUILIBRIUM MOISTURE CONTENT OF WOOD
Application Note
22
WeatherLink for Vantage Pro2, Vantage Vue, and Perception
Introduction
For any given combination of temperature and relative humidity conditions, there is an equilibrium moisture
content (EMC) for a piece of wood.
For example, if the temperature is 75 degrees F and steady, and the relative humidity is 51% and steady, then
the moisture content of a piece of wood will reach 9.3% and remain there. By remaining at a set moisture
content, the wood is said to be at “equilibrium” with the environment. If a piece of wood is introduced into
this temperature and humidity environment, and its starting moisture content is higher than 9.3%, then its
moisture content will decrease over time and approach the equilibrium value of 9.3%.
See Table 1 for an estimate of wood equilibrium moisture content at various atmospheric temperatures and
relative humidities. WeatherLink® will report this value for a Perception station or any other weather station
set to run as a Perception. However, stations set as Vantage Pro2™ and Vantage VUE™ stations will
automatically show EMC in the Browser and Plots. WeatherLink uses Inside Temperature and Inside
Humidity to calculate EMC in all cases.
(View Table 1 on next page.)
1
Temperature (in degrees F)
RELATIVE HUMIDITY (%)
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
30
1.3
2.4
3.5
4.4
5.3
6.3
7.2
8.0
8.8
9.7
10.5
11.4
12.5
13.7
15.1
16.7
18.3
20.4
21.6
22.0
35
1.3
2.6
3.7
4.7
5.5
6.3
7.1
7.9
8.8
9.6
10.5
11.4
12.3
13.5
14.9
16.5
18.3
20.4
21.6
22.0
40
1.2
2.4
3.5
4.6
5.5
6.4
7.1
7.9
8.6
9.5
10.4
11.2
12.3
13.4
14.8
16.6
18.3
20.4
21.6
22.0
45
1.3
2.4
3.5
4.4
5.3
6.3
7.2
7.9
8.6
9.4
10.2
11.1
12.2
13.3
14.7
16.4
18.3
20.4
21.6
22.0
50
1.5
2.8
3.7
4.6
5.4
6.3
7.2
7.9
8.7
9.4
10.2
11.1
12.1
13.3
14.7
16.3
18.6
20.4
21.6
22.0
55
1.3
2.7
3.8
4.7
5.5
6.3
7.0
7.8
8.6
9.5
10.3
11.0
12.2
13.4
14.8
16.3
18.2
20.4
21.6
22.0
60
1.3
2.5
3.7
4.7
5.5
6.3
7.0
7.8
8.6
9.4
10.2
11.1
12.0
13.2
14.6
16.3
18.2
20.4
21.6
22.0
65
1.2
2.6
3.5
4.5
5.4
6.2
7.0
7.8
8.5
9.3
10.2
11.0
11.9
13.3
14.4
16.6
18.2
20.4
21.6
22.0
70
1.2
2.5
3.7
4.5
5.5
6.2
7.0
7.7
8.4
9.2
10.1
11.0
11.8
13.1
14.4
16.1
17.9
20.4
21.6
22.0
75
1.2
2.3
3.5
4.5
5.2
6.0
6.9
7.6
8.4
9.2
10.0
10.9
11.8
12.9
14.3
16.0
18.1
20.4
21.6
22.0
80
1.1
2.4
3.5
4.5
5.3
6.0
6.8
7.5
8.3
9.1
9.8
10.7
11.7
12.8
14.3
15.9
17.9
20.4
21.6
22.0
85
1.1
2.0
3.4
4.3
5.2
6.0
6.6
7.5
8.2
9.0
9.8
10.7
11.6
12.5
14.2
15.7
17.6
20.0
21.6
22.0
90
1.3
2.3
3.3
4.3
5.1
5.9
6.7
7.4
8.1
9.0
9.7
10.5
11.4
12.5
14.0
15.5
17.3
19.7
21.6
22.0
95
1.3
2.3
3.2
4.1
5.0
5.7
6.5
7.2
8.1
8.8
9.5
10.5
11.4
12.4
13.9
15.3
17.4
19.8
21.6
22.0
100
1.0
2.4
3.4
4.1
5.1
5.7
6.4
7.2
8.0
8.7
9.4
10.3
11.2
12.4
13.5
15.0
17.0
19.6
21.5
22.0
105
1.1
2.2
3.3
4.2
4.8
5.6
6.4
6.9
7.8
8.7
9.4
10.3
11.1
12.3
13.5
15.1
16.9
19.0
21.6
22.0
110
1.3
2.3
3.2
4.0
4.7
5.4
6.2
6.8
7.6
8.4
9.2
9.9
10.8
12.0
13.3
14.8
16.6
19.0
21.6
22.0
115
1.1
2.1
3.1
3.9
4.6
5.3
6.1
6.7
7.6
8.2
9.1
9.9
10.7
11.9
13.1
14.4
16.2
19.0
21.6
22.0
120
1.1
2.3
3.0
3.9
4.6
5.3
6.0
6.6
7.4
8.1
9.0
9.7
10.5
11.7
12.9
14.1
16.2
18.5
21.4
22.0
125
1.0
2.0
3.0
3.7
4.5
5.2
5.8
6.6
7.2
7.9
8.7
9.6
10.5
11.5
12.7
14.0
15.7
18.4
21.3
22.0
130
1.0
2.0
3.0
3.7
4.4
5.0
5.6
6.4
7.0
7.8
8.5
9.4
10.2
11.3
12.5
13.8
15.6
18.0
21.2
22.0
140
0.0
0.0
2.8
3.5
4.1
4.8
5.5
6.1
6.8
7.5
8.2
9.0
9.8
10.9
11.9
13.4
15.1
17.5
20.7
22.0
150
0.0
0.0
0.0
3.2
3.8
4.5
5.1
5.7
6.4
7.2
7.8
8.6
9.4
10.3
11.5
13.0
14.5
16.6
20.2
22.0
160
0.0
0.0
0.0
0.0
3.7
4.2
4.9
5.4
6.1
6.8
7.4
8.2
9.1
9.9
11.0
12.3
13.8
16.2
19.8
22.0
170
0.0
0.0
0.0
0.0
3.3
4.0
4.6
5.2
5.7
6.5
7.2
7.8
8.6
9.6
10.6
11.8
13.6
15.3
19.4
22.0
180
0.0
0.0
0.0
0.0
0.0
3.8
4.4
4.8
5.4
6.0
6.8
7.4
8.1
9.0
10.1
11.4
12.9
15.0
18.1
22.0
190
0.0
0.0
0.0
0.0
0.0
3.6
4.2
4.6
5.2
5.7
6.3
7.0
7.7
8.8
9.6
10.9
12.7
14.2
17.7
22.0
200
0.0
0.0
0.0
0.0
0.0
3.3
3.9
4.4
4.8
5.3
6.0
6.6
7.4
8.4
9.4
10.8
12.1
14.0
17.3
22.0
210
0.0
0.0
0.0
0.0
0.0
0.0
3.6
4.1
4.6
5.1
5.7
6.3
7.1
8.0
9.0
10.3
11.7
13.8
16.9
22.0
Table 1. Equilibrium Moisture Content of Wood (in %).
Document Part Number: 93004.322
Rev: C (July 26, 2011)
For Vantage Pro2 Stations: #6152, 6152C, 6153, 6162, 6162C, 6163
For Vantage Pro2 ISS’s: #6322, 6322C, 6323, 6327, 6327C, 6328
For Vantage Vue Stations: #6250
For Perception II Stations: #7400
For WeatherLink: #7855, 7862
For WeatherLink: #6510SER, 6510USB, 6520, 6555
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Equilibrium Moisture Content of Wood
2